1. Field of the Invention
The present invention is directed generally to industrial and commercial lighting control panels, and more particularly to solid state lighting panels such as are commonly mounted in cabinets and that are capable of sequentially energizing a plurality of LED lighting panels at the zero crossing points of the sinusoidal input line voltage and ramping up luminous intensity within each panel or group of co-powered panels.
2. Description of the Related Art
Lighting panels are a common device found in every mid to large scale community across the United States. In many cases, a single lighting panel may be configured to energize dozens if not hundreds of individual lighting devices. If these lighting devices are energized simultaneously, this may cause a sudden spike of so-called “inrush current” which may be harmful not only to the panel but also to the upstream power line source and the downstream lighting devices as well.
Inrush current is generally a momentary current surge in an electrical device occurring when the power control device is first activated. The term is also sometimes used to refer to the maximum, instantaneous input current drawn by an electrical device when first turned on. Although inrush current typically reduces to a lower steady-state device current during continued normal device operation, the effect of significant inrush current can be highly detrimental to downstream components. For example, inrush currents can generate undesirable EMI/RFI, damage device components, lower supply voltage available to other circuits, decrease power efficiency, cause system errors, make devices difficult to control, and complicate device design. For example, if the input power source for a device is current limited or has poor load regulation, large inrush currents can cause the input voltage to drop significantly, thereby affecting overall device operation.
In addition to downstream devices and apparatus being adversely affected, the upstream power line source may also be adversely affected. Large and sudden increases in load may reduce the voltage across an entire power line or power distribution circuit. Furthermore, when this type of load occurs simultaneously in many areas, such as when darkness sets in and street lights are turned on around an entire region, even the power plant may find it difficult to maintain both proper frequency and voltage on the AC power lines.
Recognizing the detrimental effects of sudden power demands such as are brought about by excessive inrush current upon start up of electrical devices and apparatus, many utilities set electrical rates based upon peak current draw. Within the service areas of these utility companies, if inrush current causes a spike in power draw the utility customer may be subjected to electric rates that are far higher than other comparable utility customers will pay.
While many devices are subject to problematic inrush currents, some types of motors, many types of traditional lighting, power converters, and power supplies often have particularly elevated inrush currents. Recognizing a need in the marketplace, several artisans have designed devices and apparatus that can reduce the amount of inrush current drawn by various other devices. Exemplary U.S. and Foreign patents and published applications, the teachings which are incorporated herein by reference, include: U.S. Pat. No. 5,119,014 by Kronberg, entitled “Sequential power-up circuit”; U.S. Pat. No. 9,095,023 by Deppe et al, entitled “LED retrofit lamp”; and WO 2014/135875 by Giles, entitled “Dimmer switches suitable for LED lamps”. For example, Kronberg describes sequential initiation of devices to reduce peak inrush current. It is a subject of the present invention to alleviate this problematic inrush current-effect.
In addition to the foregoing patents, Webster's New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein.